1. Field of the Invention
The present invention relates to a method for processing a ring type piezoelectric device, which is applied in a piezoelectric sensor, wherein the piezoelectric sensor is applied in a torque sensor; more particularly, the present invention relates to a ring type piezoelectric device which is formed in one piece.
2. Description of the Related Art
The piezoelectric effect is a process of converting electrical energy into mechanical energy. This effect was first discovered in 1880 by the Curie brothers. In 1947, S. Roberts discovered the influence caused by a direct current electric field to BaTiO3 ceramic residual polarization, thereby triggering the applications and studies of ceramic materials in the aspect of piezoelectric effects. Nowadays, piezoelectric elements have been widely applied in various elements, such as sensors, actuators, transducers, and SAW filters. Because there are many types of piezoelectric elements, they can be classified as single layer or multi layer elements, according to their different structures, and rectangular, disk type or ring type (annular) elements, according to their different shapes.
The most important element of ring type piezoelectric elements is a ring type piezoelectric device. The manufacturing process of a conventional ring type piezoelectric device includes: respectively performing polarization of the same direction P1 to a plurality of square piezoelectric embryos 11a-14a; arranging the square piezoelectric embryos as shown in FIG. 1A; respectively processing the square piezoelectric embryos into fan-shaped piezoelectric embryos 11b-14b; and putting the fan-shaped piezoelectric embryos together as a ring shape, shown in FIG. 1B.
The polarization direction of the abovementioned conventional piezoelectric device does not surround an annular direction; that is, the polarization direction is not perpendicular to an annular cross sectional surface. Therefore, the potential disadvantages comprise: poor piezoelectric output, instability, and fragility of the structure.
Generally, a conventional torque sensor, composed of a plurality of small and rounded quartz piezoelectric materials arranged in an annular shape, cannot be formed in one piece. Therefore, the conventional torque sensor has a complex manufacturing process that is relatively lengthy.
Therefore, there is a need to provide a ring type piezoelectric device, method for processing the same, and torque sensor assembled with the same to mitigate and/or obviate the aforementioned problems.